Segment-switched 2,5 kW inverter for grid connected photovaltaic plants

In EFP94 the reported inverter efficiency was >98% over a wide operating range. In summary, the work with the stair-step principle in Section 2, Design 1, WP3 (Prototype redesign), showed that the expected high efficiency (>98%) with the stair-step principle not was obtainable, using commercial components. The reason for the difference between what was obtained with the EFP94 inverter and the actual inverter is the significantly lower power level of 2.5kW compared with 10-100kW in EFP94. Also, the losses for the commercially available MOSFET transistors, used in the switch modules, are higher than for the special bonded type used in EFP94 project. The efficiency for the 'Breadboard 1 'inverter was measured to 97%, refer to the reports Figure 4-4. Due to the experience obtained with the segment-switched principle under the first project activities, according to the project plan, it was decided to implement this new knowledge in an inverter construction, which operates on the basis of a single switch module. The improved efficiency, which might be achieved with the segment-switched principle, did not justify the corresponding number of components, considerable larger dimensions, and the increased cost required for this principle. The efficiency obtained with the 'Breadboard 1' inventer with 3 swith modules was not found to be significant better than what was obtained for a design based on a single switch module. It is therefore concluded that the 'Breadboard 2' inverter is a more optimal solution because of its smaller size and component count, and lower cost